Zdeněk Peroutka

New Configuration of Traction Converter With Medium-Frequency Transformer Using Matrix Converters

This paper presents a new configuration of a main traction converter with a medium-frequency transformer (MFT) using matrix converters intended for locomotives and particularly for suburban units supplied by a 25-kV/50-Hz and/or 15-kV/16.7-Hz ac electrification system. Single-phase matrix converters are employed in the primary medium-voltage converter which is directly connected to the ac trolley line. The output of the primary ac/ac converter supplies the primary side of the MFT. The proposed MFT-based topology of the traction converter replaces the bulky main line transformer found on board railway vehicles. Particularly in countries with a catenary of 15 kV/16.7 Hz, very low catenary frequency results in huge and heavy traction transformers. The developed topology is a power electronics solution that considerably reduces weight and losses in a traction propulsion system. The proposed converter configuration with cascaded matrix converters on the primary side of the MFT presents a new research direction in the field of traction converters with MFTs. This paper describes in detail the proposed power circuit and the control of the traction converter. The behavior of the traction converter configuration has been analyzed using simulations and experimental tests carried out on a developed low-voltage laboratory prototype of a traction converter with a rated power of 4 kVA. Based on extensive simulation and experimental study, this paper reviews the benefits, drawbacks, and constraints of the developed traction converter configuration.

Advantages of Square-Root Extended Kalman Filter for Sensorless Control of AC Drives

This paper is concerned with a fixed-point implementation of the extended Kalman filter (EKF) for applications in sensorless control of ac motor drives. The sensitivity of the EKF to round-off errors is well known, and numerically advantageous implementations based on the square-root decomposition of covariance matrices have been developed to address this issue. However, these techniques have not been applied in the EKF-based sensorless control of ac drives yet. Specific properties of the fixed-point implementation of the EKF for a permanent-magnet synchronous motor (PMSM) drive are presented in this paper, and suitability of various square-root algorithms for this case is discussed. Three square-root algorithms-Bierman-Thorton, Carlson-Schmidt-Givens, and Carlson-Schmidt-Householder-were implemented, and their performances are compared to that of the standard implementation based on full covariance matrices. Results of both simulation studies and experimental tests performed on a developed sensorless PMSM drive prototype of rated power of 10.7 kW are presented. It was confirmed that the square-root algorithms improve the behavior of the sensorless control in critical operating conditions such as low speeds and speed reversal. In particular, the Carlson-Schmidt-Givens algorithm was found to be well suited for the considered drive.

Optimal control and identification of model parameters of traction interior permanent magnet synchronous motor drive

This paper deals with a design of control of gearless wheel mounted drives of trams with interior permanent magnet synchronous motors (IPMSMs). The proposed control is based on a field oriented control linked to a rotor flux and optimally utilizes the reluctance component of torque in order to achieve maximum motor efficiency in entire speed range. For the optimal control, the stator inductances have to be known. Consequently, the three methods of their measurement were tried and compared. The first identifies motor inductances under steady-state conditions with freewheeling rotor. The second one has presented rotor locked rotor method technique which applies voltage pulses and the last one operates also with locked rotor, but a sinusoidal three-phase voltage source is used. The proposed drive control has been verified by experimental tests carried out on developed laboratory prototype of IPMSM.

Current reference generator for 50-Hz and 16.7-Hz shunt active power filters

This article describes a high-performance reference signal generator for shunt-type active power filters in frequency-variant environments. First, it extracts the fundamental frequency component from the distorted load current. The actual current reference is obtained by subtracting the recofundamental harmonic from the measured load current, and inverting the resulting harmonics waveform before feeding it to a current-controlled IGBT inverter section. To achieve a high-quality fundamental sinusoid estimation and real-time computational efficiency, our reference generator employs an adaptive and predictive multiplicative general parameter finite impulse response (MGP-FIR) band pass filter designed by evolutionary programming. Detailed procedures of MGP-FIR filtering and evolutionary optimisation are discussed. Presented theoretical conclusions are verified by simulation results and experiments performed on a designed laboratory prototype of the single-phase active power filter of rated power of 5.75 kVA. This is the first article reporting any kind of prototyping results with the MGP-FIR system.

Reduced-order square-root EKF for sensorless control of PMSM drives

Performance of square-root extended Kalman filter (EKF) based on reduced order models for sensorless control of permanent magnet synchronous motor (PMSM) drives is studied. The reduced order model of PMSM has two-dimensional state vector comprising of: (i) electrical rotor speed, and (ii) electrical rotor position. These state quantities are estimated by the EKF without either speed or position sensor on the motor shaft. The reduction of the model order results in dramatic speed-up of calculation of the estimator which takes only a few tens of microseconds on a conventional fixed-point digital signal processor. Accuracy of the estimator is improved using square-root representation of the covariance matrix. Due to its low computational requirements, the proposed square-root EKF estimator is eligible for sophisticated diagnostics as well for sensorless control of PMSM drive in a wide range of industrial applications. Presented theoretical conclusions are verified by both simulations and experiments carried out on developed PMSM drive prototype of rated power of 10.7kW.

Improved Stability of DC Catenary Fed Traction Drives Using Two-Stage Predictive Control

Control of the main propulsion drive of a traction vehicle must secure excellent drive dynamics, but it also has to consider properties of the dc catenary. Specifically, the catenary voltage is subject to short circuits, fast changes, harmonics, and other disturbances that can vary in a wide range. Therefore, the drive is equipped by the catenary input LC filter. The filter is almost undamped by design in order to achieve maximum efficiency, and the control strategy needs to secure active damping of the filter to guarantee stability of the drive. Existing solutions for active damping usually introduce some drawback in dynamic properties of the drive. In this paper, we study the use of two-stage predictive control. Damping of the filter will be solved on a long horizon using a linear controller. Dynamic properties of the drive will be guaranteed by optimization on a short horizon using the finite control set model predictive control (FCS-MPC). These two approaches can be elegantly combined via approximate dynamic programming. The resulting algorithm can be interpreted as a standard FCS-MPC with a model-based designed cost function. Performance of the resulting controller was verified in simulations on a prototype of a main permanent-magnet synchronous motor drive of a tram and experimentally on a developed laboratory prototype of 10.7 kW.

Design of new diesel-electric power supply unit for military vehicles

This paper introduces a new designed diesel-electric power-supply unit developed for military purposes. The power-supply unit is divided to two main electric parts, (i) input part which is composed of a sensorless controlled active voltage source rectifier supplied by a permanent magnet synchronous generator, and (ii) output part which is composed of a four-leg three-phase voltage source inverter with a sinusoidal LC filter with the output voltage controlled by a proportional-resonant controllers bank. The proper function of both parts of the supply unit has been verified by simulations as well as on laboratory prototypes of the devices.

Single-Phase Current-Source Active Rectifier for Traction Applications: New Control Strategy Based on Phase Shift Controller

Abstract This paper deals with the single-phase current-source active rectifier dedicated for reconstruction of older types of d.c. machine locomotives operating on both a.c. trolley wire voltages of 25 kV/50 Hz and 15 kV/16 2/3 Hz. This contribution presents new control strategy of the current-source active rectifier using controller of phase shift angle (φ) between the trolley wire voltage and current. Regarding possible interaction with railway track circuits and due to the low switching frequency, the converter employs synchronous PWM. This paper describes in detail proposed converter control and presents simulation results of the laboratory prototype. The simulation results and theoretical conclusions are verified by experiments performed on designed low voltage laboratory prototype of traction current-source active rectifier of rated power of 7 kVA.

Resolver motivated sensorless rotor position estimation of wound rotor synchronous motors

This paper presents a novel approach to sensorless control of wound rotor synchronous motor drives. The proposed rotor position estimation strategy is motivated by principle function of a resolver and utilizes design similarity between the controlled motor and the resolver based rotor position sensor. The rotor circuit is fed by controlled three-phase bridge rectifier which produces an ac component of frequency of 300Hz in the rotor excitation (flux) current. This ac component of rotor excitation current can be understood like an injection signal. Its response on the stator is evaluated by phase-lock-loop (PLL) which estimates the rotor position. This paper describes physical principle and functionality of the proposed sensorless rotor position estimation technique and verifies the theoretical foundations by simulation and experimental results made on developed drive prototype of rated power of 10kW.

Active suppression of low-frequency disturbances on AC side of traction active current-source rectifier

This paper deals with traction active current-source rectifier (ACSR) developed within the research into a new generation of main traction converters employing medium-frequency transformer dedicated for suburban units operating on both ac electrification systems of 25kV/50 Hz and 15kV/16⅔ Hz. The new control strategy able to operate under distorted trolley-wire voltage and actively suppress (i) low-frequency disturbances in trolley-wire current caused by distorted trolley-wire voltage, and (ii) input LC filter oscillations is presented. Proper function of proposed control strategy has been verified by simulations and large experimental study made on designed small-scale prototype of ACSR of rated power of 7kVA.